Adaptive Fail-Safe Power-On Control Circuit

Abstract

A circuit includes an input for receiving power from an external power supply, a voltage regulator coupled to the power input and providing regulated voltage to an external circuit and to the power supply control circuit itself, and a first switch coupled between ground and an Enable input of the voltage regulator. A control input of the first switch is coupled to the regulated voltage, such that when the voltage regulator provides regulated voltage, the first switch is closed, coupling the Enable input to ground, keeping the voltage regulator active. A first switching circuit provides manual activation and deactivation of the voltage regulator; a second switching circuit provides automatic activation of the voltage regulator whenever the power input becomes powered. An intervening circuit prevents the second switching circuit from activating the voltage regulator when the first switching circuit has deactivated it, despite the continued presence of the external power supply.

What is claimed is: 
     
         1 . An audio source selection circuit for selecting between first and second audio inputs, the selection circuit comprising:
 a first input receiving an indication that the first audio input is active;   a second input receiving an indication that the second audio input is active; and   a third input receiving an indication that the first audio input is prioritized over the second audio input, and in response, lowering the volume of the second audio input or disconnecting the second audio input.   
     
     
         2 . The selection circuit of  claim 1 , wherein the first audio input is for an intercom system. 
     
     
         3 . The selection circuit of  claim 2 , wherein the second audio input is for Bluetooth audio or wired auxiliary audio. 
     
     
         4 . The selection circuit of  claim 3 , wherein the second audio input is lowered in response to the third input receiving the indication that the first audio input is prioritized over the second audio input. 
     
     
         5 . The selection circuit of  claim 3 , wherein the second audio input is disconnected in response to the third input receiving the indication that the first audio input is prioritized over the second audio input. 
     
     
         6 . The selection circuit of  claim 1 , wherein the second audio input is lowered in response to the third input receiving the indication that the first audio input is prioritized over the second audio input. 
     
     
         7 . The selection circuit of  claim 1 , wherein the second audio input is disconnected in response to the third input receiving the indication that the first audio input is prioritized over the second audio input. 
     
     
         8 . The selection circuit of  claim 1 , further comprising:
 a fourth input receiving an indication that a third audio input is active; and   a fifth input receiving an indication that the second audio input is prioritized over the third audio input, and in response, lowering the volume of the third audio input or disconnecting the third audio input.   
     
     
         9 . The selection circuit of  claim 8 , wherein the second audio input is Bluetooth audio and the third audio input is wired auxiliary audio. 
     
     
         10 . The selection circuit of  claim 8 , wherein the second audio input is wired auxiliary audio and the third audio input is Bluetooth audio. 
     
     
         11 . A method of audio source selection between first and second audio inputs, the method comprising:
 receiving a first indication that the first audio input is active;   receiving a second indication that the second audio input is active; and   receiving a third indication that the first audio input is prioritized over the second audio input, and in response, lowering the volume of the second audio input or disconnecting the second audio input.   
     
     
         12 . The method of  claim 11 , wherein the first audio input is for an intercom system. 
     
     
         13 . The method of  claim 12 , wherein the second audio input is for Bluetooth audio or wired auxiliary audio. 
     
     
         14 . The method of  claim 13 , wherein the second audio input is lowered in response to receiving the third indication. 
     
     
         15 . The method of  claim 13 , wherein the second audio input is disconnected in response to receiving the third indication. 
     
     
         16 . The method of  claim 11 , wherein the second audio input is lowered in response to receiving the third indication. 
     
     
         17 . The method of  claim 11 , wherein the second audio input is disconnected in response to receiving the third indication. 
     
     
         18 . The method of  claim 11 , further comprising:
 receiving a fourth indication that a third audio input is active; and   receiving a fifth indication that the second audio input is prioritized over the third audio input, and in response, lowering the volume of the third audio input or disconnecting the third audio input.   
     
     
         19 . The method of  claim 18 , wherein the second audio input is Bluetooth audio and the third audio input is wired auxiliary audio. 
     
     
         20 . The method of  claim 18 , wherein the second audio input is wired auxiliary audio and the third audio input is Bluetooth audio.